Organic anti-reflective coating polymers, anti-reflective coating composition comprising the same and preparation methods thereof

ABSTRACT

An organic anti-reflective polymer which prevents back reflection of lower film layers and eliminates standing wave that is occurred by a thickness change of photoresist and light, in a process for fabricating ultrafine patterns that use photoresist for lithography by using 193 nm ArF and its preparation method. More particularly, the organic anti-reflective polymer of the present invention is useful for fabricating ultrafine patterns of 64M, 256M, 1G, and 4G DRAM semiconductor devices. A composition containing such organic anti-reflective polymer, an anti-reflective coating layer made therefrom and a preparation method thereof.

This is a divisional of U.S. application Ser. No. 10/037,552, filed Jan.4, 2002.

BACKGROUND

1. Technical Field

An organic anti-reflective polymer which prevents back reflection oflower film layers and eliminates standing wave that occurs as a resultof thickness changes of photoresist and light, in a process forfabricating ultrafine patterns that use photoresist for lithography byusing 193 nm ArF and its preparation method are disclosed. Moreparticularly, the organic anti-reflective polymer is disclosed that isuseful for fabricating ultrafine patterns of 64M, 256M, 1G, and 4G DRAMsemiconductor devices. A composition containing such organicanti-reflective polymer, an anti-reflective coating layer made therefromand a preparation method thereof are also disclosed.

2. Description of the Background Art

In a fabrication process of ultrafine patterns for preparingsemiconductor devices, standing waves and reflective notching inevitablyoccur due to the optical properties of lower film layer on the wafer anddue to the thickness change of photosensitive film. In addition, thereis another problem of the CD (critical dimension) alteration caused bydiffracted and reflected light from the lower film layers. Thus, it hasbeen suggested to introduce anti-reflective coating that enablespreventing back reflection at a lower film layer by introducing organicmaterial showing high absorbance at a wavelength range of the lightemployed as a light source.

Anti-reflective coating is classified into inorganic and organicanti-reflective coating depending upon the material used, or intoabsorptive and interfering anti-reflective coating based on theoperation mechanism. For microlithography using I-line (365 nmwavelength) radiation, inorganic anti-reflective coating ispredominantly used, while TiN and amorphous carbon as absorptive systemand SiON as interfering system are employed.

In a fabrication process of ultrafine patterns using KrF laser, SION hasbeen mainly used as an inorganic anti-reflective film. However, in thecase of an inorganic anti-reflective film, no material has been knownwhich enables the control of the interference at 193 nm, the wavelengthof light source. Thus, there has been great deal of efforts to employ anorganic compound as an anti-reflective coating.

To be a good organic anti-reflective coating, the following conditionsmust be satisfied:

(1) Peeling of the photoresist layer due to the dissolution in a solventmust not take place when conducting a lithographic process. In order toachieve this goal, a molded coating must be designed to form across-linked structure without producing any chemical as a by-product.

(2) Chemicals such as acid or amine must not migrate into or out fromthe anti-reflective coating. This is because when acid migrates fromanti-reflective coating, undercutting occurs at a lower part of thepattern while footing may occur when a base such as amine migrates.

(3) The etching speed of the anti-reflective coating should be fasterthan that of the upper photosensitive film so as to facilitate etchingprocess by using photosensitive film as a mask.

(4) Therefore, the anti-reflective coating must be as thin as possibleto an extent to sufficiently play a role as an anti-reflective coating.

The existing organic anti-reflective material is mainly divided into twotypes, specifically, (1) polymers containing chromophore, cross-linkingagent (single molecule) cross-linking the polymers and an additive(thermally variable oxidant) and (2) polymers which can cross link bythemselves and contain chromophore and an additive (thermally variableoxidant). But these two types of anti-reflective material have a problemin that the control of k value is almost impossible because the contentof the chromophore is defined according to the ratio as originallydesigned at the time of polymerization. Thus, if it is desired to changethe k value, it must be synthesized again.

SUMMARY OF THE DISCLOSURE

A novel organic polymer for anti-reflective coating and its preparationmethod are disclosed.

An anti-reflective coating composition comprising the aforementionedpolymer and a preparation method thereof are also disclosed.

Semiconductor devices on which a pattern is formed from such ananti-reflective coating by submicrolithography are also disclosed.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The following compounds having Formulas 1 and 2, respectively areprovided which can be used in an anti-reflective coating.

In the above Formulas 1:

R_(a), R_(b) are each independently hydrogen or methyl;

R′, R″ are each independently —H, —OH, —OCOCH₃, —COOH, —CH₂OH, orsubstituted or unsubstituted, or straight or branched alkyl or alkoxyalkyl having 1 to 6 carbon atoms;

n represents an integer selected from 1, 2, 3, 4 and 5;

x, y each represents mole fraction from 0.01 to 0.99.

Further, in the above Formulas 2: R₁₀ and R₁₁ are each independentlystraight or branched substituted C₁₋₁₀ alkoxy alkyl; and

R₁₂ is hydrogen or methyl.

The compound of Formula 2 is prepared by polymerizing (meth)acrolein toobtain poly(meth)acrolein followed by reacting the obtained polymericproduct with branched or straight substituted alkyl alcohol having 1 to10 carbon atoms.

In detail, (meth)acrolein is first dissolved in an organic solvent andadded thereto a polymerization initiator to carry out polymerizationunder vacuum at 60 to 70° C. for 4 to 6 hours. Then, the obtainedpolymeric product is reacted with branched or straight substituted alkylalcohol having 1 to 10 carbon atoms in the presence oftrifluoromethylsulfonic acid as a catalyst at a room temperature for 20to 30 hours.

In the above process, suitable organic solvent is selected from thegroup consisting of tetrahydrofuran (THF), cyclohexanone,dimethylformamide, dimethylsulfoxide, dioxane, methylethylketone,benzene, toluene, xylene and mixtures thereof. As a polymerizationinitiator, it can be mentioned 2,2-azobisisobutyronitrile (AIBN),benzoylperoxide, acetylperoxide, laurylperoxide, t-butylperacetate,t-butylhydroperoxide or di-t-butylperoxide. A preferred example of saidalkyl alcohol having 1 to 10 carbon atoms is ethanol or methanol.

A preferred compound of Formula 2 is selected from the group consistingof the compounds of the following Formulas 3 to 6.

The above compounds of Formulas 3 to 6 are readily cured in the presenceof acid and other polymers having alcohol group.

The polymer of Formula 1 is prepared by reacting acetoxystyrene monomer,hydroxyalkylacrylate monomer in an organic solvent and then polymerizingthe obtained compound with a polymerization initiator. Any conventionalorganic solvent can be used in this process but a preferred solvent isselected from the group consisting of tetrahydrofuran, toluene, benzene,methylethylketone, dioxane and mixtures thereof. As a polymerizationinitiator, any conventional radical polymerization initiator can be usedbut it is preferred to use a compound selected from the group consistingof 2,2′-azobisisobutyronitrile, acetylperoxide, laurylperoxide, andt-butylperoxide. The above polymerization reaction is preferably carriedout at a temperature ranging from about 50 to 90° C. and the mole ratioof each monomer is in the range of 0.01˜0.99:0.01˜0.99.

An anti-reflective coating composition comprises a polymer of Formula 1and a polymer of Formula 2.

A preparation method of an organic anti-reflective coating comprises thesteps of dissolving a polymer of Formula 1 and a compound of Formula 2in an organic solvent, filtering the obtained solution, coating thefiltrate on a lower layer and hard-baking the coated layer. Further, anyconventional organic solvent can be used in this process but a preferredsolvent is selected from the group consisting of ethyl3-ethoxypropionate, methyl 3-methoxypropionate, cyclohexanone, andpropyleneglycolmethylether acetate. It is preferred that theaforementioned solvent is used in an amount ranging from about 200 toabout 5,000 wt. % based on the total weight of the anti-reflectivecoating resin used. The preferred temperature range for hard-bakingranges from about 100 to about 300° C.

A semiconductor device prepared from any of the aforementionedanti-reflective coating compositions of the present invention.

Two monomer(acetoxystyrene monomer, hydroxyalkylacrylate monomer) havinga large sized chromophore was first synthesized to enable for a polymermade therefrom to achieve a high absorbance at the wavelength of 193 nm.Further, in order to allow improved properties to a produced organicanti-reflective coating, such as good molding property, air-tightness,and dissolution resistance, an epoxy group was introduced to raise across linking reaction during a hard-baking step following a coatingstep. The obtained polymer is referred to as a primary polymer (thecompound of Formula 1). In addition, a secondary polymer (the compoundof Formula 2), a compound capable of forming a cross linkage upon thereaction with an alcohol group in resin was also synthesized to form across-linked product with the primary polymer by a thermal reaction

In particular, the cross-linking agents used are in the form of apolymer are designed to maximize the efficiency of the cross-linkingreaction. Especially, it is possible to freely adjust the k value of theanti-reflective film by controlling the proportion of the primarypolymer, laurylperoxide, and t-butylperoxide. The above polymerizationreaction is preferably carried out at a temperature ranging from about50 to 90° C. and the mole ratio of each monomer is in the range of0.01˜0.99:0.01˜0.99.

An anti-reflective coating composition comprises a polymer of Formula 1and a polymer of Formula 2.

A preparation method of an organic anti-reflective coating comprises thesteps of dissolving a polymer of Formula 1 and a compound of Formula 2in an organic solvent, filtering the obtained solution, coating thefiltrate on a lower layer and hard-baking the coated layer. Further, anyconventional organic solvent can be used in this process but a preferredsolvent is selected from the group consisting of ethyl3-ethoxypropionate, methyl 3-methoxypropionate, cyclohexanone, andpropyleneglycolmethylether acetate. It is preferred that theaforementioned solvent is used in an amount ranging from about 200 toabout 5,000 wt. % based on the total weight of the anti-reflectivecoating resin used. The preferred temperature range for hard-bakingranges from about 100 to about 300° C.

A semiconductor device prepared from any of the aforementionedanti-reflective coating compositions of the present invention.

Two monomer(acetoxystyrene monomer, hydroxyalkylacrylate monomer) havinga large sized chromophore was first synthesized to enable for a polymermade therefrom to achieve a high absorbance at the wavelength of 193 mn.Further, in order to allow improved properties to a produced organicanti-reflective coating, such as good molding property, air-tightness,and dissolution resistance, an epoxy group was introduced to raise across linking reaction during a hard-baking step following a coatingstep. The obtained polymer is referred to as a primary polymer (thecompound of Formula 1). In addition, a secondary polymer (the compoundof Formula 2), a compound capable of forming a cross linkage upon thereaction with an alcohol group in resin was also synthesized to form across-linked product with the primary polymer by a thermal reaction

In particular, the cross-linking agents used are in the form of apolymer are designed to maximize the efficiency of the cross-linkingreaction. Especially, it is possible to freely adjust the k value of theanti-reflective film by controlling the proportion of the primarypolymer,

Further, the anti-reflective coating resin has a good solubility in allof the hydrocarbon solvents while has a dissolution resistance in any ofthe solvents during a hard-baking step. In addition, no undercutting orfooting is experienced in the fabrication process of patterns.Especially, because the anti-reflective coating resin is made fromacrylate polymer which enables higher etching speed relative to that ofthe photosensitive film during etching process, the etching selectivityis improved.

The following examples are set forth to illustrate more clearly theprinciples and practice of the disclosure to a person skilled in theart. As such, they are not intended to limit the disclosure, but areillustrative of certain preferred embodiments.

EXAMPLES Example 1 Composition ofpoly[acetoxystyrene-(2-hydroxyethylacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 2-hydroxyethylacrylate while stirring and 300g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(2-hydroxyethylacrylate)] resin of the followingFormula 7 (yield: 82%).

Example 2 Composition ofpoly[acetoxystyrene-(3-hydroxypropylacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 3-hydroxypropylacrylate while stirring and300 g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(3-hydroxypropylacrylate)] resin of the followingFormula 8 (yield: 80%).

Example 3 Composition ofpoly[acetoxystyrene-(4-hydroxybutylacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 4-hydroxybutylacrylate while stirring and 300g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(4-hydroxybutylacrylate)] resin of the followingFormula 9 (yield: 79%).

Example 4 Composition ofpoly[acetoxystyrene-2-hydroxyethylmethacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 2-hydroxyethylmethacrylate while stirring and300 g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(2-hydroxyethyllmethacrylate)] resin of thefollowing Formula 10 (yield: 83%).

Example 5 Composition ofpoly[acetoxystyrene-(3-hydroxypropylmethacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 3-hydroxypropylmethacrylate while stirringand 300 g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(3-hydroxypropylmethacrylate)] resin of thefollowing Formula 11 (yield: 84%).

Example 6 Composition ofpoly[acetoxystyrene-(4-hydroxybutylmethacrylate)]copolymer

A 500 ml round bottom flask was charged with 0.1 mole ofacetoxystyrene/0.1 mole of 4-hydroxybutylmethacrylate while stirring and300 g of separately prepared tetrahydrofuran was added to a completemixture. Thereafter, 0.1˜3.0 g of 2,2′-azobisisobutyronitrile was addedto allow a polymerization reaction at 60 to 75° C. under a nitrogenatmosphere for 5 to 20 hours. After the completion of the reaction, theobtained solution was precipitated with ethyl ether or n-hexane solventand then filtered and dried to obtainpoly[acetoxystyrene-(4-hydroxybutylmethacrylate)] resin of the followingFormula 12 (yield: 78%).

Example 7 Preparation of an Anti-reflective Coating Solution

A polymer of Formula 1 as prepared in one of Examples 1 to 6 and apolymer of Formula 2 were dissolved in propyleneglycolmethyletheracetate(PGMEA). The obtained solution was filtered, coated on a wafer,and hard-baked at 100˜300° C. for 10˜1,000 seconds. Then, aphotosensitive film was applied thereon and followed by a routineultrafine pattern fabrication process.

The cross-linking agent used is in the form of a polymer is designed tomaximize the cross-linking efficiency. Further, it is possible to freelymodify the k value of an organic anti-reflective coating by controllingthe proportion of a primary polymer. Thus, the present inventionovercomes the prior art problem wherein the control of a k value was notpossible.

Moreover, the anti-reflective coating resin includes two monomer havinglarge sized chromophores, one of the chromophores has an effect ofprotecting undercutting due to unbalance of acidity after making a filmowing to a weak basic, that enables a polymer made therefrom to achievea high absorbance at the wavelength of 193 nm.

Further, the anti-reflective coating resin dissolves well in allhydrocarbon solvent, while does not dissolve in any of the solventsduring a hard-baking step and it does not experience undercutting andfooting in a fabrication process of patterns. Particularly, because theanti-reflective coating resin is composed of acrylate polymer, itsetching speed is higher than that of a photosensitive film and thus, theetching selectivity can be improved.

The present invention has been described in an illustrative manner, andit is to be understood the terminology used is intended to be in thenature of description rather than of limitation. It must be understoodthat many modifications and variations of the present invention arepossible in light of the above teachings. Therefore, it is to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

1. An anti-reflective coating composition compound having the structureof the following Formula I and a compound of the following Formula 2:

wherein: R_(a), R_(b) are each independently hydrogen or methyl; R′ andR″ are each independently selected from the group consisting of —H, —OH,—OCOCH₃, —COOH, —CH₂OH, alkyl having 1 to 6 carbon atoms and alkoxyalkyl having 1 to 6 carbon atoms; n is an integer ranging from 1 to 5;and x and y each represent mole fractions ranging from 0.01 to 0.99;

wherein, R₁₀ and R₁₁ are each independently C₁₋₁₀ alkoxy alkyl, and R₁₂is hydrogen or methyl.
 2. The anti-reflective coating of claim 1 whereinthe compound of Formula 1 ispoly[acetoxystyrene-(2-hydroxyethylacrylate)].
 3. The anti-reflectivecoating of claim 1 wherein the compound of Formula 1 ispoly[acetoxystyrene-(3-hydroxypropylacrylate)].
 4. The anti-reflectivecoating of claim 1 wherein the compound of Formula 1 ispoly[acetoxystyrene-(4-hydroxybutylacrylate)].
 5. The anti-reflectivecoating of claim 1 wherein the compound of Formula 1 ispoly[acetoxystyrene-(2-hydroxyethyllmethacrylate)].
 6. Theanti-reflective coating of claim 1 wherein the compound of Formula 1 ispoly[acetoxystyrene-(3-hydroxypropylmethacrylate)].
 7. Theanti-reflective coating of claim 1 wherein the compound of Formula 1 ispoly[acetoxystyrene-(4-hydroxybutylmethacrylate)].
 8. A method forpreparing an anti-reflective coating comprising: dissolving a compoundof Formula 1 as follows and a compound of Formula 2 in an organicsolvent to obtain a solution; filtering the solution to obtain afiltrate; coating the filtrate onto a lower layer of the substrateresulting in a coated layer disposed on the lower layer; and hard-bakingthe coated layer;

wherein: R_(a), R_(b) are each independently hydrogen or methyl; R′ andR″ are each independently selected from the group consisting of —H, —OH,—OCOCH₃, —COOH, —CH₂OH, alkyl having 1 to 6 carbon atoms and alkoxyalkyl having 1 to 6 carbon atoms; n is an integer ranging from 1 to 5;and x and y each represent mole fractions ranging from 0.01 to 0.99. 9.The method according to claim 8, wherein said organic solvent isselected from the group consisting of ethyl-3-ethoxypropionate, methyl3-methoxypropionate, cyclohexanone, and propyleneglycolmethyletheracetate.
 10. The method according to claim 8, wherein said organicsolvent is used in an amount ranging from about 200 to about 5,000 wt. %based on the total weight of the anti-reflective coating resin used. 11.The method according to claim 8, wherein the hard-baking step is carriedout at a temperature ranging from about 100 to about 300° C.
 12. Asemiconductor device prepared from the anti-reflective coatingcomposition of claim
 1. 13. A semiconductor device prepared from theanti-reflective coating composition of claim
 2. 14. A semiconductordevice prepared from the anti-reflective coating composition of claim 3.15. A semiconductor device prepared from the anti-reflective coatingcomposition of claim
 4. 16. A semiconductor device prepared from theanti-reflective coating composition of claim
 5. 17. A semiconductordevice prepared from the anti-reflective coating composition of claim 6.18. A semiconductor device prepared from the anti-reflective coatingcomposition of claim 7.